Cydia isn't appearing in loader?

I jailbroke my ipodtouch (4.2.1 firmware) with greenpois0n and the jailbreak worked fine but when i turned on my ipod and went to the loader nothing was in there. I tried several times and the loader either crashes or nothing shows up (cydia is supposed to so i can download it). I tried using i-fun-box and iphonebrowser to delete the com.apple.mobile.installation.plist file to make cydia appear but everytime after i do that and reboot the itouch the file is back like nothing happened. does anyone know how i can make that file go away for good or get cydia to appear in the loader? thx!